Satsuma hybrid named &#39;Sonet&#39;

ABSTRACT

A new Satsuma hybrid ( Citrus unshiu  X) designated the variety name of ‘Sonet’ is described. The novel characteristics of the fruit include early maturity, tighter rind and firmer fruit does not puff easily and has an improved flavour compared to known varieties of Satsuma ripening at this time.

BOTANICAL/COMMERCIAL CLASSIFICATION

(Citrus unshiu X), new hybrid Satsuma variety.

VARIETY DENOMINATION

‘Sonet’.

BACKGROUND OF THE INVENTION

‘Sonet’ is an open pollinated hybrid of an unpatented Citrus unshiu variety ‘Miho Wase’ (the female seed parent). In 1996 open pollinated fruit was collected from ‘Miho Wase’ trees adjacent to Citrus reticulata varieties ‘Nova tangelo’, ‘Ellendale’ and ‘Novelty’ (possible male pollen parents). The seeds from each fruit were extracted and planted. Zygotic seedlings were selected in the nursery in 1997, by leaf morphology. The 14 selected seedlings were budded to ‘Troyer citrange’ rootstocks and planted on a trellising and arching system in a forcing house, in 1998, situated at the Addo Research Station in Addo, in the Eastern Cape province of the Republic of South Africa (global positioning satellite co-ordinates 25° 42′E.; 33° 34′S.). Due to the early maturing and fruiting of citrus trees grown on the trellising and arching system, the first fruit was set in 2000. These trees were then evaluated for fruit quality traits. Based on the results of this evaluation, one of the aforementioned trees was selected for further evaluation, resulting in the present ‘Sonet’ variety. ‘Sonet’ was made subject of a South African Plant Breeders' Rights application on 5 December 2006. This application was subsequently granted in 2009 under number ZA 20094289.

The time of fruit maturity (early to mid April), makes this selection an early maturing variety. Good flavour (mandarin-like) and firm fruit with a good shelf life make ‘Sonet’ superior to the ‘Satsuma’ and early ‘Clementine’ in the market at this time.

Trees bear a good to excellent crop from the fourth year after planting. Alternate-bearing has not been noted. There is a small percentage of splitting in February and as with all early maturing mandarin cultivars, some fruit are lost to sunburn.

‘Sonet’ was first asexually propagated in Addo, South Africa in 2000 when buds were collected from a hybrid seedling designated WH/B/02/36 (1740). Three trees were topworked onto ‘Carrizo citrange’ rootstocks and one tree onto a ‘Rosehaugh’ mandarin rootstock. These four trees of ‘Sonet’ were initially used for evaluation and description purposes. Two more trees were top worked onto ‘F80/9 citrumelo’ rootstocks in 2001 for evaluation purposes. In 2005 three budded nursery trees were planted out on ‘Troyer citrange’ rootstocks for evaluation. The first trial orchard of ‘Sonet’ was planted at Addo in February 2006. This consisted of budded nursery trees, 125 trees on ‘Carrizo citrange’ rootstock and 19 trees on ‘Troyer citrange’ rootstock. In 2009 a further 24 budded nursery trees on C35 rootstock and four trees on ‘Carrizo citrange’ rootstock were planted for evaluation. All characteristics of the original tree and its fruit as determined and described appear to be transmitted through succeeding asexual propagations. No incompatibility or other rootstock related problems have yet been observed. The mother tree is still growing in the forcing house on the trellising and arching system in a 20 liter pot and is as at 2012 14 years old. The tree is in a fair condition and is still bearing good quality fruit.

Further, ‘Sonet’ has been cleansed of all graft transmissible viruses and viroids by shoot-tip grafting (STG), followed by pre-immunization with a light strain of the Citrus tristeza virus (LMS6). This was done through a regulated process, which involves taking vegetative buds from the mother tree and introducing the same into the South African Citrus Improvement Scheme. In this process, plant material is shoot-tip grafted to provide a virus-free source of bud wood material. Material so obtained is then pre-immunized with a mild strain of the aforementioned Citrus tristeza virus, followed by a certification by the Citrus Foundation Block. In addition, ‘Sonet’ is free from Apple Stem growing virus, psorosis virus, Impietratura, Citrus Viroids, Exocortis and CVD I, II, III, IV and V.

The present variety is distinguishable over ‘Miho Wase’ Satsuma (Citrus unshiu) which is as the closest variety to ‘Sonet’, in the following ways. ‘Sonet’ differs in leaf morphology from the ‘Miho Wase’, matures about two weeks later than the ‘Miho Wase’, has a smoother firmer and tighter rind, does not puff easily, and has improved flavour over ‘Miho Wase’. Fruit of ‘Sonet’ could contain some seed under cross pollination conditions, while fruit of ‘Miho Wase’ will be seedless under similar conditions.

BRIEF SUMMARY OF THE INVENTION

This invention relates to a new and distinct variety of a Satsuma hybrid (Citrus unshiu X), presently named ‘Sonet’ the novel characteristics of which, under the local South African evaluation conditions, reside particularly in the early onset of maturity of the fruit, as well as a firmer fruit rind, does not puff easily and has improved flavour over ‘Satsuma’ and early ‘Clementine’ maturing at this time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: is a photograph showing an entire ‘Sonet’ tree on ‘Carrizo citrange’ rootstock at four years of age;

FIG. 2: is a photograph showing crop load potential of ‘Sonet’ at three years of age;

FIG. 3: is a photograph of ‘Sonet’ fruit in perspective view showing its general shape;

FIG. 4: is a further photograph showing details of a typical ‘Sonet’ fruit: viewed from top and bottom aspects showing the apex and base, respectively, together with a cross section through the fruit;

FIG. 5: is a photograph depicting a typical stem of ‘Sonet’, and in particular showing bud union;

FIG. 6: is a photograph depicting a close up of the bark on ‘Sonet’;

FIG. 7: is a close-up photograph showing several leaves of ‘Sonet’, illustrating the sizes and shapes of the leaves, including the venation thereof;

FIG. 8: is a photograph showing florescence; and

FIG. 9: is a schematic illustration of the pedigree of ‘Sonet’.

DETAILED BOTANICAL DESCRIPTION

The detailed description below is based on four year old trees, unless otherwise specifically stated to the contrary.

-   Tree: ‘Sonet’ trees are compact and Satsuma-like with a     Clementine-like leaf shape. The tree is precocious and heavy     bearing. Thorns have been observed on some nursery trees and on     juvenile trees. However older bearing trees have very small to no     thorns. Observed juvenile thorniness is probably attributable to     shoot-tip grafting (STG). Thorniness appears to be reduced and in     some cases eliminated through successive growth cycles, notably     after the third successive flush. The rootstock compatibility with     ‘Carrizo citrange’ is good as observed and indicated by stem     measurements.     -   -   Size.—The average height of trees is 1.8 meters, measured             from soil level, with an average skirt height of 0.75             meters. The average spread (width) of trees is 1.5 meters.         -   Shape.—obloid in shape.         -   Trunk.—The trunk has a fairly smooth surface texture and is             brown-green (RHS ______) in color. The average trunk             diameter is 24.0 centimeters measured at the bud union.             Average diameters of 19.5 centimeters and 25.5 centimeters             were measured at heights of 15 centimeters above and below             the bud union, respectively. The average height of the bud             union is 28 centimeters, measured above soil level.         -   Branch.—Branches have a diameter of between 8.2 and 13.4             centimeters. There are between 5 and 8 main branches per             tree. Average crotch angles vary between 30° and 90°. The             smaller of the range of crotch angles is found among the             middle vertically growing branches forming the top of the             tree, and the larger of the range of crotch angles is found             between the vertically growing branches and the horizontally             growing branches, forming the sides of the tree. As with the             trunk, the branches have a fairly smooth surface texture and             are brown-green (RHS ______) in color. -   Flower:     -   -   Size and color.—The flower of ‘Sonet’ is typically             hermaphroditic. Its petals are yellow-white (RHS ______) on             the inside and yellow-white (RHS ______) with small yellow             (RHS ______) speckles on the outside. Further, it has light             yellow (RHS ______) anthers. Flowering occurs from September             to October in South Africa. Being a normal diploid Satsuma,             there is a small to medium amount of pollen with             approximately 63% viability depending on climatic             conditions, and as determined using the carmine-red stain             method. Flower buds are ovoid in shape and have an average             length of 11.5 millimeters and an average width of 6.1             millimeters. In addition, each flower has five petals.             Petals are elliptic in shape and have an average length and             width of 14.0 millimeters and 5.6 millimeters, respectively.             The petal tip is acute in shape, while the base is truncate.             The petal margin is entire. On a completely opened flower,             the typical calyx diameter averages 5.0 millimeters. There             are generally three to five flowers per cluster and the             flowers have a typical citrus flower fragrance.         -   Reproductive organs.—The style has a length of 5.5             millimeters, while the stigma and the style, in combination,             are approximately 7.2 millimeters long. The stamen has a             length of 7.4 millimeters. The style is white-green (RHS             ______), while the stigma is light yellow (RHS ______) in an             unpollinated state. On average, there is one style and             stigma, and 14 to 20 stamens with anthers. The style with             the stigma is the same length as the stamens positioning the             anthers around, at the same height as, the stigma. -   Leaves: For purposes of the following leaf description, all leaves     were taken as the first leaf after the new flush growth.     -   -   Shape and size.—Leaves are simple, brevipetiolate and             lanceolate in shape, with very slight dentate incisions             along the blade margin. Blade emargination is not present at             the tip. The leaves also have typically pinnate venation.             The shape of the leaf apex is acute while the base is             cuneate. In cross-section, the blade shape is straight but             fairly concave. The length of a typical leaf blade is             approximately 80.2 millimeters in length and the leaf blade             also has a width of approximately 28.5 millimeters. The             ratio of length:width of the typical leaf is 2.8:1.             Generally speaking, the shape and size of the 4-year old             ‘Sonet’ trees differ from the mother tree in that the leaves             are smaller and narrower in shape and are lighter in colour.         -   Petiole.—Wings are present but not prominent and are linear             and narrow. Width of the wings is 2 millimeters. Length of             the petiole is approximately 11 millimeters. -   Color and surface texture: The adaxial (leaf upper) surface is     darker (RHS ______), in comparison to the abaxial (leaf lower)     surface (RHS ______). The leaf upper and lower surfaces are smooth     and leaf veins are not prominent. -   Fruit, external characteristics:     -   -   Color.—The rind color is Yellow-green (RHS 15A and 17A) to             Yellow-orange (RHS 21A and 23 A) when the fruit is fully             mature.         -   Rind.—Fruit is easy to peel and the rind has an average             thickness of 1.5 to 2 millimeters.         -   Oil glands.—Small oil glands are present, not protruding and             are uniform in size.         -   Surface.—Pubescence is absent on the fruit surface, and the             fruit surface is fairly smooth in appearance.         -   Shape.—With reference to the Citrus descriptors of the             previously named International Plant Genetic Resources             Institute (IPGRI), now known as Biodiversity International,             the shape of ‘Sonet’ is obloid, having its broadest part in             the middle of the fruit. The general shape of the proximal             part (stem end) of the fruit is slightly rounded with a             slight ruffling around the stem, while the fruit apex             (flower end) is depressed.         -   Size.—Fruit is on average 42 millimeters in length and 65 to             85 millimeters in diameter. Individual fruit mass varies             between 68 grams to 96 grams with an average mass of 83             grams per fruit (see Table 1 below) on ‘Carrizo citrange’             rootstock. The fruit length:diameter ratio is 0.742.         -   Base.—Depressed.         -   Calyx.—Slightly rounded.         -   Apex.—Slightly rounded.         -   Areola.—Present and smooth.         -   Stylar scar.—Present, but small in size. -   Fruit, internal characteristics:     -   -   Color.—The internal flesh color is orange (RHS ______) to             dark orange (RHS ______) when the fruit is fully mature.         -   Navel.—absent when fruit is viewed internally.         -   Glandular layer.—thickness of the rag is normal and slightly             tough.         -   Mesocarp (albedo).—The adherence of the albedo to the pulp             is weak and thus the peel is reasonably easy to remove from             the pulp. No albedo strands are left behind after such             removal. The albedo color is yellow-orange (RHS ______).         -   Axis.—Fruit has an open core with a diameter of             approximately 15 millimeters. Further, the core has sparse             to no filling.         -   Segments.—Each fruit has ten to twelve segments, and on             average there are eleven well-developed segments per fruit.         -   Pulp.—The pulp is fine with large cells. In a transverse             section of the fruit, the shape of the fruit pulp is             scalloped.         -   Juice.—Fruit is juicy with a good flavor that is aligned             towards a mandarin-like flavour. Juice is yellow-orange (RHS             ______) in color. Fruit have an average juice percentage of             59.5% on ‘Carrizo citrange’ rootstock. As indicated by the             solids:acid ratio (see Table 1), the best time to harvest             fruit under South African conditions is early to mid April.         -   Seeds.—Seeds are mostly clavate in shape (about 75%),             however some are semi-deltoid in shape (about 25%), with a             mostly wrinkled surface. In this regard, approximately 30%             of the seed surface tends to be smooth. The clavate shaped             seeds have an average length of 10.3 millimeters and an             average width of 4.8 millimeters, while the semi-deltoid             shaped seeds have an average length of 8.0 millimeters and             an average width of 6.0 millimeters. Further, the seeds have             a grey-white (RHS ______) external color, and are green (RHS             ______) and highly poly-embryonic after removal of the             testa. This variety is parthenocarpic. However it contains             few (1 to 3) to no seeds in solid blocks (as seen in Table             1). In mixed blocks where cross pollination is present,             fruit do contain more seed.

TABLE 1 ‘Sonet’ Satsuma hybrid: Internal Quality Tests - 2010 (trees 4 years old, planted in 1996) Addo, Eastern Cape, South Africa: Percentage fruit with Avg. Fruit Root- Juice Brix Acid Brix:Acid 0 1-3 4-6 7+ Mass Cultivar stock Test date % % % Ratio seed per fruit (grams) ‘Sonet’ Carrizo 24 Mar. 2010 60.0 12.0 1.34  9.0 62 18 5 3 79.1 ‘Sonet’ Carrizo 20 Apr. 2010 59.0 12.6 1.00 12.6 54  8 0 1 85.5

TABLE 2 Internal Quality Tests (trees topworked in 2000 to ‘Carrizo citrange’ rootstocks) Addo, Eastern Cape, South Africa: Test Date Juice % Brix % T. Acid % Brix/TA Ratio 14 Apr. 2008 67.4 11.8 1.08 10.9 09 Apr. 2010 58.2 9.8 1.05 9.3

-   -   -   Yield.—The average fruit yields across the time period             2009-2010 appear in Table 3 below:

TABLE 3 Average Fruit Yield (2009-2010) Addo, Eastern Cape, South Africa: Year 2009 2010 Tree age (years) 3 4 Yield (kg fruit/tree) 20.1 32.9 Yield (ton/ha) 11.1 18.3

The fruit of ‘Sonet’ is intended for human consumption. Fruit stored and shipped at 4° C., and kept under these conditions, are likely to keep for up to six weeks. Data of a cold sterilization trial indicate that 91% of the fruit is marketable after storage for 32 days at −0.5 Celsius and 7 days at ambient temperature. Optimal protocols for degreening and waxing is required for extension of shelf life.

The above-described new variety of Satsuma hybrid displays a distinct early expression of maturity (early to mid April), as well as an improved flavour and firmer fruit and tighter rind and does not puff easily, compared to known varieties of Satsuma ripening at this time. 

What we claim is:
 1. A novel and distinct Satsuma hybrid tree having the characteristics described and illustrated herein. 